Manchester United winger Bebe, currently on loan at Turkish giants Besiktas, has torn his anterior cruciate ligament.

The 21-year-old is now set to miss six months of action after sustaining the injury while playing for Portugal Under-21s against Slovakia on Tuesday.

Besiktas said in a statement: "A scan has shown an anterior cruciate ligament tear to his left knee and he will be unable to play for six months. Surgery is required and we have contacted Manchester United and there will be a joint decision about where the operation will be done."

Bebe made the switch to Besiktas on a season-long loan during June, with the deal reported to be worth around £875,000.

He joined United in a shock £7.4 million deal from Portuguese club Vitoria de Guimaraes last summer, and Sir Alex Ferguson admitted at the time he had never seen the player in action.

His first season at Old Trafford was a testing one, as he made just seven first-team appearances and came under fire for a lack of guile on the ball.

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